Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a solar cell and a preparation method thereof, and a photovoltaic module. The solar cell comprises a substrate and a passivation contact structure. Wherein the substrate is provided with a first surface and a second surface which are oppositely arranged along the thickness direction of the substrate; the passivation contact structure is arranged on the first surface of the substrate; the passivation contact structure comprises a tunneling oxide layer and a polycrystalline silicon layer arranged on one side, deviating from the substrate, of the tunneling oxide layer; the polycrystalline silicon layer comprises at least one first doped polycrystalline silicon layer; the carbon doping amount of the first doped polycrystalline silicon layer is gradually increased along the direction gradually away from the substrate. According to the passivation contact structure in the solar cell provided by the invention, by inserting the carbon-containing first doped polycrystalline silicon layer of which the carbon doping amount increases progressively into the polycrystalline silicon layer, the polycrystalline silicon layers in different regions can have different H distribution states, so that the concentration of H in the tunneling oxide layer is effectively avoided, and finally the purposes of reducing the film explosion rate and improving the performance of the solar cell are achieved. And the phenomenon of membrane explosion of the battery is reduced.

Description

Technical Field

[0001] The present application relates to the photovoltaic field, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Tunnel Oxide Passivated Contact solar cell (TOPCon) has a stacked structure of high-quality ultra-thin silicon oxide and heavily doped polysilicon, which achieves efficient passivation of the entire back surface, while carriers are selectively collected. It has the advantages of simple preparation process, no photoinduced degradation problem when using N-type silicon wafers, and compatibility with traditional high-temperature sintering technology.

[0003] Plasma enhanced chemical vapor deposition (PECVD) is a technology suitable for large-scale preparation of doped polysilicon layer on the back of TOPCon solar cells because it has the following advantages: rapid deposition of in-situ doped amorphous silicon (a-Si:H) at low temperature, easy control of large-area uniform deposition, and easy subsequent cleaning of amorphous silicon deposited by slight plating. The market share of using PECVD to prepare doped polysilicon layer on the back of TOPCon solar cells is increasing year by year. However, under high-temperature annealing conditions, H in amorphous silicon film diffuses into the tunneling oxide layer SiO2 and silicon substrate in the TOPCon cell structure, and the diffusion coefficient of H2 in SiO2 under high-temperature annealing conditions (about 900°C) is much greater than its diffusion coefficient in crystalline silicon, which ultimately leads to a large amount of H accumulation in the tunneling oxide layer (SiO2) layer and cannot enter the silicon substrate or escape from the surface in time, resulting in stress concentration in the tunneling oxide layer (SiO2) and eventually rupture. After the film is exploded, the passivation structure of the solar cell is destroyed, and its passivation performance and electrical performance will decrease. Summary of the invention

[0004] Based on this, it is necessary to provide a solar cell with a lower film explosion rate and a preparation method thereof, and a photovoltaic module.

[0005] An embodiment of the present application provides a solar cell, including a substrate and a passivation contact structure;

[0006] Wherein, the substrate has a first surface and a second surface which are arranged opposite to each other along the thickness direction thereof;

[0007] The passivation contact structure is disposed on the first surface of the substrate;

[0008] The passivation contact structure comprises a tunneling oxide layer and a polysilicon layer arranged on a side of the tunneling oxide layer away from the substrate;

[0009] The polysilicon layer includes at least one first doped polysilicon layer;

[0010] The carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

[0011] In one embodiment, the carbon doping amount of the first doped polysilicon layer is 2×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0012] In one embodiment, the polysilicon layer further includes at least two first doped polysilicon layers, and the at least two first doped polysilicon layers include stacked first doped polysilicon sublayers and second doped polysilicon sublayers in a direction gradually away from the substrate.

[0013] In one embodiment, the first doped polysilicon layer satisfies one or both of the following conditions:

[0014] (1) The carbon doping amount in the first doped polysilicon sublayer is 2×10 18 atoms / cm 3 ~6×10 18 atoms / cm 3 ;

[0015] (2) The carbon doping amount in the second doped polysilicon sublayer is 6×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0016] In one of the embodiments, the concentration of the P-type or N-type doping element in the first doped polysilicon layer increases gradually in a direction away from the substrate.

[0017] In one embodiment, the polysilicon layer further includes at least one second doped polysilicon layer, and the second doped polysilicon layer is disposed on a side of the first doped polysilicon layer away from the substrate.

[0018] In one embodiment, the solar cell further includes a first electrode, wherein the first electrode is electrically connected to the second doped polysilicon layer.

[0019] In one embodiment, the thickness of the first doped polysilicon layer and the thickness of the second doped polysilicon layer are proportional to the distance from the substrate.

[0020] Furthermore, the present application provides a method for preparing a solar cell, comprising the following steps:

[0021] Providing a substrate having a first surface and a second surface disposed opposite to each other along a thickness direction of the substrate;

[0022] forming a tunneling oxide layer on the first surface of the substrate;

[0023] Forming a polysilicon layer on a side of the tunnel oxide layer away from the substrate;

[0024] The polysilicon layer includes a first doped polysilicon layer, and the carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

[0025] The present application also provides a photovoltaic assembly, wherein a power supply device thereof includes the solar cell as described above or the solar cell manufactured by the above manufacturing method.

[0026] The passivation contact structure in the solar cell provided in the present application can make the polysilicon layer in different areas have different H distribution states by inserting a first carbon-doped polysilicon layer with an increasing carbon doping amount into the polysilicon layer, thereby effectively avoiding the concentration of H in the tunneling oxide layer, and ultimately reducing the film explosion rate and reducing the phenomenon of film explosion in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the solar cell structure provided in Example 1 of the present application.

[0028] Description of reference numerals:

[0029] 10: solar cell; 100: N-type silicon substrate; 110: tunneling oxide layer; 120: first doped polysilicon layer; 121: first doped polysilicon sublayer; 122: second doped polysilicon sublayer; 1211: first doped sublayer; 1212: second doped sublayer; 1221: third doped sublayer; 1222: fourth doped sublayer; 130: second doped polysilicon layer; 140: first anti-reflection layer; 150: first electrode; 160: P-type emitter; 170: aluminum oxide layer; 180: second anti-reflection layer; 190: second electrode. DETAILED DESCRIPTION

[0030] The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly understood. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0032] Unless otherwise indicated, all percentages, fractions and ratios are calculated based on the total mass of the composition of the present application. Unless otherwise indicated, all masses of the listed ingredients are given as active substances, so they do not include solvents or by-products that may be contained in commercially available materials. The term "mass percentage content" herein can be represented by the symbol "%".

[0033] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0034] Unless mentioned to the contrary, terms in the singular may include plural forms and should not be construed as being one in number.

[0035] As used herein, "includes," "comprising," "containing," "having," or other variations are intended to encompass non-closed inclusions, and no distinction is made between these terms. The term "comprising" means that other steps and ingredients that do not affect the end result may be added. The term "comprising" also includes the terms "consisting of" and "consisting essentially of." The compositions and methods / processes of the present application include, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. As used herein, no distinction is made between the terms "efficacy," "performance," "effect," and "efficacy."

[0036] The words "preferably", "more preferably" and the like in this application refer to embodiments of the present application that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or in other circumstances. In addition, the statement of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of this application.

[0037] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0038] An embodiment of the present application provides a solar cell, including a substrate and a passivation contact structure;

[0039] Wherein, the substrate has a first surface and a second surface which are arranged opposite to each other along the thickness direction thereof;

[0040] The passivation contact structure is disposed on the first surface of the substrate;

[0041] The passivation contact structure includes a tunneling oxide layer and a polysilicon layer arranged on a side of the tunneling oxide layer away from the substrate;

[0042] The polysilicon layer includes at least one first doped polysilicon layer;

[0043] The carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

[0044] The passivation contact structure in the solar cell provided in the present application can make the polysilicon layer in different areas have different H distribution states by inserting a first carbon-doped polysilicon layer with an increasing carbon doping amount into the polysilicon layer, thereby effectively avoiding the concentration of H in the tunneling oxide layer, and ultimately reducing the film explosion rate and reducing the phenomenon of film explosion in the battery.

[0045] It can be understood that the first doped polysilicon layer contains carbon elements and P-type or N-type doping elements, and the carbon doping amount and carbon doping concentration in the present application have the same meaning.

[0046] In a specific example, the carbon doping amount of the first doped polysilicon layer is 2×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0047] In a specific example, the concentration of the P-type or N-type doping element in the first doped polysilicon layer is 5×10 17 atoms / cm 3 ~10 21 atoms / cm 3 .

[0048] Furthermore, along a direction gradually away from the substrate, the concentration of the P-type or N-type doping element in the first doped polysilicon layer increases gradually.

[0049] In a specific example, the polysilicon layer further includes at least two first doped polysilicon layers, and the at least two first doped polysilicon layers include stacked first doped polysilicon sublayers and second doped polysilicon sublayers in a direction gradually away from the substrate. It can be understood that the first doped polysilicon includes stacked first doped polysilicon sublayers and second doped polysilicon sublayers in a direction gradually away from the substrate.

[0050] The present application controls the distribution state of H in different regions of the polysilicon layer through multiple carbon-doped polysilicon layers with different carbon doping concentrations, thereby effectively controlling the concentration of H in the tunneling oxide layer (SiO2), and ultimately reducing the phenomenon of film explosion in the polysilicon layer.

[0051] Furthermore, the carbon doping amount in the first doped polysilicon sublayer is 2×10 18 atoms / cm 3 ~6×10 18 atoms / cm 3 The concentration of the P-type doping element or the N-type doping element in the first doped polysilicon sublayer is 5×10 17 atoms / cm 3 ~10 20 atoms / cm 3 The carbon doping amount in the second doped polysilicon sublayer is 10 20 atoms / cm 3 ~10 21 atoms / cm 3 The concentration of the P-type doping element or the N-type doping element in the second doped polysilicon sublayer is 6×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0052] It can be understood that the first doped polysilicon sublayer includes a first doped sublayer and a second doped sublayer along the direction away from the substrate, and the second doped polysilicon sublayer includes a third doped sublayer and a fourth doped sublayer along the direction away from the substrate, wherein the reaction sources of the first doped sublayer and the third doped sublayer during the preparation process include P-type or N-type doping elements but do not contain carbon elements, and the reaction sources of the second doped sublayer and the fourth doped sublayer during the preparation process include P-type or N-type doping elements and carbon elements. Taking the first doped polysilicon sublayer as an example, if only the reaction source when preparing the second doped sublayer in the first doped polysilicon sublayer includes carbon elements, then the carbon doping amount of the first doped polysilicon sublayer is the carbon doping amount of the second doped sublayer. The semiconductor doping elements of the first doped sublayer, the second doped sublayer, the third doped sublayer and the fourth doped sublayer are the same, that is, they are all P-type doped or N-type doped.

[0053] In a specific example, the concentration of the P-type or N-type doping element in the first doping sublayer is 5×10 17 atoms / cm 3 ~3×10 19 atoms / cm 3 The concentration of the P-type or N-type doping element in the first doping sublayer may be, but is not limited to, 5×10 17 atoms / cm 3 , 6×10 17 atoms / cm 3 ,7×10 17 atoms / cm 3 , 8×10 17 atoms / cm 3 ,9×10 17 atoms / cm 3 , 10 18 atoms / cm 3 , 2×10 18 atoms / cm 3 , 3×10 18 atoms / cm 3 , 4×10 18 atoms / cm 3 , 5×10 18 atoms / cm 3 , 6×10 18 atoms / cm 3 ,7×10 18 atoms / cm 3 , 8×10 18 atoms / cm 3 ,9×10 18 atoms / cm 3 , 10 19 atoms / cm 3 , 1.1×1019 atoms / cm 3 , 1.2×10 19 atoms / cm 3 , 1.3×10 19 atoms / cm 3 , 1.4×10 19 atoms / cm 3 , 1.5×10 19 atoms / cm 3 , 1.6×10 19 atoms / cm 3 , 1.7×10 19 atoms / cm 3 , 1.8×10 19 atoms / cm 3 , 1.9×10 19 atoms / cm 3 , 2×10 19 atoms / cm 3 , 2.2×10 19 atoms / cm 3 , 2.4×10 19 atoms / cm 3 , 2.6×10 19 atoms / cm 3 , 2.8×10 19 atoms / cm 3 or 3×10 19 atoms / cm 3 .

[0054] Furthermore, the carbon doping concentration in the second doped sublayer is 2×10 18 atoms / cm 3 ~6×10 18 atoms / cm 3 The concentration of P-type or N-type doping elements in the second doping sublayer is 8×10 19 atoms / cm 3 ~10 20 atoms / cm 3 .

[0055] Furthermore, the carbon doping concentration in the second doped sublayer may be, but is not limited to, 2×10 18 atoms / cm 3 , 2.1×10 18 atoms / cm 3 , 2.2×10 18 atoms / cm 3 , 2.3×10 18 atoms / cm 3 , 2.4×1018 atoms / cm 3 , 2.5×10 18 atoms / cm 3 , 2.6×10 18 atoms / cm 3 , 2.7×10 18 atoms / cm 3 , 2.8×10 18 atoms / cm 3 , 2.9×10 18 atoms / cm 3 , 3×10 18 atoms / cm 3 , 3.5×10 18 atoms / cm 3 , 4×10 18 atoms / cm 3 , 4.5×10 18 atoms / cm 3 , 5×10 18 atoms / cm 3 , 5.5×10 18 atoms / cm 3 or 6×10 18 atoms / cm 3 .

[0056] The concentration of the P-type or N-type doping element in the second doping sublayer may be, but is not limited to, 8×10 19 atoms / cm 3 , 8.5×10 19 atoms / cm 3 ,9×10 19 atoms / cm 3 , 9.5×10 19 atoms / cm 3 or 10 20 atoms / cm 3 .

[0057] In a specific example, the concentration of the P-type or N-type doping element in the third doping sublayer is 10 20 atoms / cm 3 ~2×10 20 atoms / cm 3 Furthermore, the concentration of the P-type or N-type doping element in the third doping sublayer may be, but is not limited to, 1×10 20 atoms / cm 3 , 1.1×10 20 atoms / cm 3 , 1.2×10 20 atoms / cm 3, 1.3×10 20 atoms / cm 3 , 1.4×10 20 atoms / cm 3 , 1.5×10 20 atoms / cm 3 , 1.6×10 atoms / cm 3 , 1.7×10 20 atoms / cm 3 , 1.8×10 20 atoms / cm 3 , 1.9×10 20 atoms / cm 3 or 2×10 20 atoms / cm 3 .

[0058] In a specific example, the concentration of the P-type or N-type doping element in the fourth doping sublayer is 2×10 20 atoms / cm 3 ~10 21 atoms / cm 3 The carbon doping concentration in the fourth doped sublayer is 6×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0059] Furthermore, the concentration of the P-type or N-type doping element in the fourth doping sublayer may be, but is not limited to, 2×10 20 atoms / cm 3 , 3×10 20 atoms / cm 3 , 3.2×10 20 atoms / cm 3 , 3.5×10 20 atoms / cm 3 , 3.6×10 20 atoms / cm 3 , 3.7×10 20 atoms / cm 3 , 3.8×10 20 atoms / cm 3 , 4×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 6×10 20 atoms / cm 3 , 6.1×10 20 atoms / cm 3 , 6.2×1020 atoms / cm 3 , 6.3×10 20 atoms / cm 3 , 6.4×10 20 atoms / cm 3 , 6.5×10 20 atoms / cm 3 ,7×10 20 atoms / cm 3 , 8×10 20 atoms / cm 3 ,9×10 20 atoms / cm 3 or 10 21 atoms / cm 3 The carbon doping concentration in the fourth doping sublayer may be, but is not limited to, 6×10 18 atoms / cm 3 ,7×10 18 atoms / cm 3 , 8×10 18 atoms / cm 3 , 10 19 atoms / cm 3 , 2×10 19 atoms / cm 3 , 4×10 19 atoms / cm 3 , 6×10 19 atoms / cm 3 , 8×10 19 atoms / cm 3 , 10 20 atoms / cm 3 , 2×10 20 atoms / cm 3 , 3×10 20 atoms / cm 3 , 4×10 20 atoms / cm 3 or 5×10 20 atoms / cm 3 .

[0060] When carbon is doped into polysilicon, its performance is closely related to the content of doped carbon atoms. Too high or too low a concentration of carbon doping will not allow the battery to achieve optimal performance. At the same time, after adding a single layer of carbon-doped polysilicon, the tunneling oxide layer (SiO2) interface will be damaged by carbon induction, thereby increasing its surface recombination and further increasing the composite current density. Therefore, this application further cooperates to limit the concentration of carbon doping by optimizing the polysilicon layer structure. While reducing the surface recombination caused by carbon-doped polysilicon, it can also enhance the film strength, inhibit blistering, and improve the passivation quality, ultimately improving the electrical performance of solar cells such as the opening voltage, reducing the film explosion rate of solar cells, and improving the yield of solar cells.

[0061] In a specific example, the polysilicon layer further includes at least one second doped polysilicon layer, and the second doped polysilicon layer is disposed on a side of the first doped polysilicon layer away from the substrate.

[0062] Furthermore, the concentration of the P-type or N-type doping element in the second doped polysilicon layer is 4×10 20 atoms / cm 3 ~10 21 atoms / cm 3 Specifically, the concentration of the P-type or N-type doping element in the second doped polysilicon layer may be, but is not limited to, 4×10 20 atoms / cm 3 , 4.5×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 5.5×10 20 atoms / cm 3 , 6×10 20 atoms / cm 3 , 6.5×10 20 atoms / cm 3 ,7×10 20 atoms / cm 3 , 7.5×10 20 atoms / cm 3 , 8×10 20 atoms / cm 3 , 8.5×10 20 atoms / cm 3 ,9×10 20 atoms / cm 3 or 10 21 atoms / cm 3 .

[0063] In a specific example, the thickness of the first doped polysilicon layer and the thickness of the second doped polysilicon layer are proportional to the distance from the substrate. Further, the thickness of the first doped polysilicon layer is 1nm-40nm, and the thickness of the second doped polysilicon layer is 30nm-100nm.

[0064] Furthermore, the thickness of the first doped polysilicon sublayer is 1 nm to 20 nm, and the thickness of the first doped polysilicon sublayer is 6 nm to 30 nm.

[0065] It can be understood that the thickness of the first doped sublayer, the second doped sublayer and the fourth doped sublayer are each independently 1 nm to 10 nm, specifically, the thickness of the first doped sublayer, the second doped sublayer and the fourth doped sublayer are each independently but not limited to 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm. The thickness of the third doped sublayer is 5 nm to 20 nm, specifically, the thickness of the third doped sublayer is each independently but not limited to 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm or 20 nm.

[0066] The thickness of the second doped polysilicon layer may be independently, but is not limited to, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0067] In a specific example, the material of the tunnel oxide layer may be, but is not limited to, silicon oxide. The thickness of the tunnel oxide layer is 1.5 nm to 2 nm. The substrate is an N-type substrate or a P-type substrate. Further, the substrate is an N-type silicon substrate.

[0068] In a specific example, the solar cell further includes a first electrode electrically connected to the second doped polysilicon layer.

[0069] Furthermore, the solar cell of the present application further includes a first anti-reflection layer, and the first anti-reflection layer is arranged between the first electrode and the passivation contact structure.

[0070] Furthermore, the solar cell further includes an emitter, which is disposed on the second surface.

[0071] In a specific example, a passivation layer and a second anti-reflection layer are also provided on the emitter electrode and are stacked in a direction away from the substrate. Further, the solar cell further includes a second electrode in contact with the second anti-reflection layer.

[0072] It can be understood that either the first surface or the second surface is a light-receiving surface, and the other surface is a backlight surface. Specifically, the first surface is a light-receiving surface, and the second surface is a backlight surface; or the first surface is a backlight surface, and the second surface is a light-receiving surface. The first surface and the second surface may also be a suede structure as required, and further, the surface corresponding to the light-receiving surface is a suede structure.

[0073] The present application provides a method for preparing a solar cell as described above, comprising the following steps:

[0074] Providing a substrate, the substrate having a first surface and a second surface disposed opposite to each other along a thickness direction thereof;

[0075] forming a tunneling oxide layer on the first surface of the substrate;

[0076] Forming a polysilicon layer on a side of the tunnel oxide layer facing away from the substrate;

[0077] The polysilicon layer includes a first doped polysilicon layer, and the carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

[0078] Furthermore, the polysilicon layer also includes at least two first doped polysilicon layers, and the at least two first doped polysilicon layers include stacked first doped polysilicon sublayers and second doped polysilicon sublayers in a direction gradually away from the substrate. The conditions for preparing at least two first doped polysilicon layers include: using doping source gas, silane and carbon source gas as gas sources, and using chemical vapor deposition to sequentially form at least two first doped polysilicon layers at the same vacuum degree and temperature; wherein, from the beginning of the reaction, as the reaction time increases, the flow rate of the carbon source gas increases. It can be understood that the flow rate of the carbon source gas in preparing the first doped polysilicon sublayer is greater than the flow rate of the carbon source gas in preparing the second doped polysilicon sublayer.

[0079] Specifically, the preparation of the solar cell includes the following steps: providing a substrate on which a passivation contact structure is to be deposited, and preparing a tunneling oxide layer;

[0080] Preparing a first doped polysilicon sublayer and a second doped polysilicon sublayer on the tunneling oxide layer;

[0081] Among them, the conditions for preparing the first doped polysilicon sublayer and the second doped polysilicon sublayer independently include: preparing by plasma enhanced chemical vapor deposition in an atmosphere containing doping source gas, silane, hydrogen and methane with a flow ratio of (1sccm~8sccm): (1sccm~8sccm): (2sccm~12sccm): (3sccm~20sccm).

[0082] Specifically, the conditions for preparing the second doped sublayer and the fourth doped sublayer independently include: preparing by plasma enhanced chemical vapor deposition in an atmosphere containing 1 sccm~8 sccm of a doping source gas containing a P-type or N-type doping element, 1 sccm~8 sccm of silane, 2 sccm~12 sccm of hydrogen and 3 sccm~20 sccm of methane.

[0083] In a specific example, the conditions for preparing the first doped sublayer, the third doped sublayer and the second doped polysilicon layer independently include: preparing by plasma enhanced chemical vapor deposition in an atmosphere containing a doping source gas containing P-type or N-type doping elements with a flow ratio of (1sccm~8sccm): (2sccm~12sccm): (3sccm~20sccm), silane and hydrogen.

[0084] Specifically, the conditions for preparing the first doped sublayer, the third dopant and the second doped polysilicon layer independently include: preparing by plasma enhanced chemical vapor deposition in an atmosphere containing 1 sccm~8 sccm of a doping source gas containing a P-type or N-type doping element, 1 sccm~8 sccm of silane and 2 sccm~12 sccm of hydrogen.

[0085] In a specific example, the conditions for preparing the first doped sublayer, the second doped sublayer, the third doped sublayer, the fourth doped sublayer and the second doped polysilicon layer each independently include: the radio frequency power is 3W~9W.

[0086] The radio frequency power for preparing the first doped sublayer, the third doped sublayer and the second doped polysilicon layer is independently 3 W to 7 W. The radio frequency power for preparing the second doped sublayer and the fourth doped sublayer is independently 5 W to 9 W.

[0087] Specifically, the RF power for preparing the first doped sublayer, the third doped sublayer and the second doped polysilicon layer is independently 3 W, 4 W, 5 W, 6 W or 7 W. The RF power for preparing the second doped sublayer and the fourth doped sublayer is independently 5 W, 6 W, 7 W, 8 W or 9 W.

[0088] The present application also provides a photovoltaic assembly, the power supply device of which includes the solar cell as described above.

[0089] The solar cell and its preparation method of the present application are further described in detail below in conjunction with specific examples. The raw materials used in the following examples are all commercially available products unless otherwise specified.

[0090] Example 1

[0091] like Figure 1As shown, this embodiment provides a solar cell 10, including an N-type silicon substrate 100, the N-type silicon substrate 100 has a light-receiving surface and a backlight surface, the surface of the light-receiving surface is a velvet structure, and the backlight surface includes a passivation contact structure stacked in sequence, the passivation contact structure includes a tunneling oxide layer 110, a first doped polysilicon layer 120 and a second doped polysilicon layer 130 stacked in sequence, wherein the first doped polysilicon layer 120 includes a first doped polysilicon sublayer 121 and a second doped polysilicon sublayer 122 stacked on the tunneling oxide layer 110. The first doped polysilicon sublayer 121 includes a first doped sublayer 1211 and a second doped sublayer 1212 stacked in a direction away from the substrate; the second doped polysilicon sublayer 122 includes a third doped sublayer 1221 and a fourth doped sublayer 1222 stacked in a direction away from the substrate; the second doped polysilicon layer 130 includes a first anti-reflection layer 140 and a first electrode 150 stacked in a direction away from the substrate, and includes a P-type emitter 160, an aluminum oxide layer 170, a second anti-reflection layer 180 and a second electrode 190 stacked in sequence on the light-receiving surface, wherein the second electrode 190 contacts the second anti-reflection layer 180, and the first electrode 150 contacts the second doped polysilicon layer 130;

[0092] The method for preparing the passivation contact structure comprises the following steps:

[0093] 1. In a 13.56MHz RF PECVD system, plasma-assisted N2O oxidation is used to grow nano-SiO with high-purity N2O. x The oxidation power was set to 5 W, the oxidation time was set to 80 s, and the thickness was 1.8 nm.

[0094] 2. First doped sublayer: reaction power is set to 5W, SiH4 gas flow is fixed to 5sccm, PH3 gas flow is set to 1.5sccm, H2 flow is set to the ratio of total flow, H2 flow / total flow is 0.3, thickness is 5nm, and the doping concentration of phosphorus in the first doped sublayer is 1.9e19 atoms / cm 3 ;

[0095] 3. Second doped sublayer: reaction power is set to 6W, PH3 gas flow is set to 1.5sccm, SiH4 gas flow is 5sccm, CH4 flow is 5sccm, H2 flow is set to the ratio of total flow, H2 flow / total flow is 0.3, thickness is 5nm, and the doping concentration of phosphorus in the second doped sublayer is 9.7e19 atoms / cm 3 The carbon doping concentration in the second doped sublayer is 4e18 atoms / cm 3 ;

[0096] 4. The third doped sublayer: the reaction power is set to 5W, the SiH4 gas flow rate is fixed to 5sccm, the PH3 gas flow rate is set to 3sccm, the H2 flow rate is set to the ratio of the total flow rate, the H2 flow rate / total flow rate is 0.4, the thickness is 10nm, and the phosphorus doping concentration in the third doped sublayer is 1.8e20 atoms / cm 3 ;

[0097] 5. Fourth doped sublayer: reaction power is set to 7W, PH3 gas flow is set to 3sccm, SiH4 gas flow is 5sccm, CH4 flow is 10sccm, H2 flow is set to the ratio of total flow, H2 flow / total flow is 0.4, thickness is 5nm, and the doping concentration of phosphorus in the fourth doped sublayer is 3.6e20 atoms / cm 3 The carbon doping concentration in the fourth doped sublayer is 7e18 atoms / cm 3 ;

[0098] 6. Fifth doped sublayer: reaction power is set to 5W, SiH4 gas flow is fixed to 5sccm, PH3 gas flow is set to 9sccm, H2 flow is set to the ratio of total flow, H2 flow / total flow is 0.9, thickness is 80nm, and the doping concentration of phosphorus in the fifth doped sublayer is 5e20 atoms / cm 3 .

[0099] Example 2

[0100] The difference from Example 1 is that the reaction power in the fourth doped sublayer is set to 6W, the PH3 gas flow rate is set to 3sccm, the CH4 flow rate is 15sccm, the H2 flow rate is set to a ratio of the total flow rate, the H2 flow rate / total flow rate is 0.4, the thickness is 5nm, and the phosphorus doping concentration in the fourth doped sublayer is 6.3e20 atoms / cm 3 The carbon doping concentration in the fourth doped sublayer is 4e19 atoms / cm 3 .

[0101] Example 3

[0102] The difference from Example 1 is that the reaction power in the fourth doped sublayer is set to 6W, the PH3 gas flow rate is set to 3sccm, the CH4 flow rate is 18sccm, the H2 flow rate is set to a ratio of the total flow rate, the H2 flow rate / total flow rate is 0.4, the thickness is 5nm, and the phosphorus doping concentration in the fourth doped sublayer is 6.2e20 atoms / cm 3 The carbon doping concentration in the fourth doped sublayer is 4e20 atoms / cm 3 .

[0103] Example 4

[0104] The difference from Embodiment 1 is that no second doped polysilicon layer is provided.

[0105] Example 5

[0106] The difference from Example 1 is that the carbon doping concentration in the first doped polysilicon sublayer is adjusted to 1e20 atoms / cm 3 .

[0107] Comparative Example 1

[0108] The difference from Example 1 is that the polysilicon layer is not doped with carbon. During the preparation of the polysilicon layer, the reaction power is set to 5W, the SiH4 gas flow rate is fixed to 5sccm, the PH3 gas flow rate is set to 9sccm, the H2 flow rate is set to a ratio of the total flow rate, the H2 flow rate / total flow rate is 0.9, the thickness is 120nm, and the phosphorus doping concentration is 5e20 atoms / cm 3 .

[0109] Battery performance of each embodiment and each comparative example

[0110] Battery performance test is based on standard test conditions: irradiance 1000W / m 2 , battery temperature (CellTemperature) 25℃, air mass (Air Mass) AM1.5.

[0111] Yield test method: AOI appearance cracked film camera inspection after annealing. Install AOI camera inspection at the annealing discharge port, and the unqualified films will be automatically sent to the NG discharge port for inspection. Yield = (total number - number of defective films) / total number.

[0112] The values ​​of the doping concentrations in the embodiments and comparative examples specifically correspond to the doping concentrations of the surfaces of the layers on one side away from the substrate.

[0113] The performance of the batteries of the above embodiments and comparative examples are summarized in Table 1 below.

[0114] Table 1

[0115]

[0116] From the above-mentioned embodiments and comparative examples, it can be seen that the solar cell in the embodiment provided with a carbon-doped polysilicon layer has a significantly improved yield compared with the conventional solar cell in comparative example 1. Further comparison of the embodiment solar cells shows that in embodiment 4, the doped polysilicon layer is not provided with two carbon-doped polysilicon layers, and the cell yield decreases to a certain extent compared with embodiments 1-3. Even though two carbon-doped layers are provided in embodiment 5, the carbon doping concentration in the carbon-doped layer close to the substrate is higher than that in the carbon-doped layer far from the substrate, and the H distribution is not effectively optimized. Therefore, not only the yield of the battery is reduced, but also the performance of the battery is reduced to a certain extent.

[0117] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0118] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solutions of the present application in detail, but cannot be understood as limiting the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the contents of the attached claims, and the description can be used to interpret the contents of the claims.

Claims

1. A solar cell, characterized in that: including a substrate and a passivation contact structure; Wherein, the substrate has a first surface and a second surface which are arranged opposite to each other along the thickness direction thereof; The passivation contact structure is disposed on the first surface of the substrate; The passivation contact structure comprises a tunneling oxide layer and a polysilicon layer arranged on a side of the tunneling oxide layer away from the substrate; The polysilicon layer includes at least one first doped polysilicon layer; The carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

2. The solar cell according to claim 1, wherein: The carbon doping amount of the first doped polysilicon layer is 2×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

3. The solar cell according to claim 1 or 2, characterized in that: The polysilicon layer further includes at least two first doped polysilicon layers, wherein the at least two first doped polysilicon layers include a first doped polysilicon sublayer and a second doped polysilicon sublayer stacked in a direction gradually away from the substrate.

4. The solar cell according to claim 3, characterized in that The first doped polysilicon layer satisfies one or both of the following conditions: (1) The carbon doping amount in the first doped polysilicon sublayer is 2×10 18 atoms / cm 3 ~6×10 18 atoms / cm 3 ; (2) The carbon doping amount in the second doped polysilicon sublayer is 6×10 18 atoms / cm 3 ~5×10 20 atoms / cm 3 .

5. The solar cell according to claim 1 or 2, characterized in that: In a direction gradually away from the substrate, the concentration of the P-type or N-type doping element in the first doped polysilicon layer increases gradually.

6. The solar cell according to claim 1 or 2, characterized in that: The polysilicon layer further includes at least one second doped polysilicon layer, and the second doped polysilicon layer is disposed on a side of the first doped polysilicon layer away from the substrate.

7. The solar cell according to claim 6, characterized in that The solar cell further includes a first electrode electrically connected to the second doped polysilicon layer.

8. The solar cell according to claim 6, wherein: The thickness of the first doped polysilicon layer and the thickness of the second doped polysilicon layer are proportional to the distance from the substrate.

9. A method for preparing a solar cell, characterized in that: The following steps are involved: Providing a substrate having a first surface and a second surface disposed opposite to each other along a thickness direction of the substrate; forming a tunneling oxide layer on the first surface of the substrate; Forming a polysilicon layer on a side of the tunnel oxide layer away from the substrate; The polysilicon layer includes a first doped polysilicon layer, and the carbon doping amount of the first doped polysilicon layer increases gradually in a direction gradually away from the substrate.

10. A photovoltaic module, characterized in that: The power supply device comprises the solar cell according to any one of claims 1 to 8 or the solar cell prepared by the preparation method according to claim 9.

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